The invention pertains to a pipe cleaning machine for driving spiral wire rods by means of a hollow shaft connected to a drive motor, the hollow shaft being supported in a machine housing. The shaft acts on a rotary coupling with at least two coupling jaws, which are supported in recesses of a jaw holder rotatably attached to the hollow shaft. The recesses are bounded by parallel surfaces, the jaws being supported in such a way that they are able to move in both the radial and axial directions. The jaws can also be pressed against the spiral wire rod under the action of a control device.
Pipe cleaning machines of this type with two coupling jaws are described in DE-PS 27 14 124. Spiral wire rods are helical springs which are relatively stiff in the torsional sense but are otherwise flexible; these are also known. Several of them can be connected together by means of specially designed couplings and can be guided through the hollow shaft of the pipe cleaning machine. At the extreme forward end of these spiral wire rods, various cleaning tools can be attached, which serve to drill out or cut off dirt inside a pipeline, which can have many twists and turns. Such tools include, for example, square bits, circular saws, spinning chains, milling heads, etc. It is also possible to pass pressure hoses through the spiral wire rods, so that an additional flushing action can be generated in the area of the cleaning tool.
The operator of these pipe cleaning machines and spiral wire rods must have a great deal of skill. By turning the motor on and off, by engaging and releasing the friction coupling, and possibly also by reversing the direction of rotation, he must control the action of the cleaning tool in such a way that it makes the necessary progress through the pipeline but at the same time does not become jammed in it. The operator must control not only the pipe cleaning machine but also the spiral wire rod, which he must do by hand. For this purpose, he holds the spiral wire rod in front of the pipe cleaning machine, bending it into an arc before it enters the pipeline. He then exerts pressure on the arc so as to decrease its length. Thus the operator acquires a sense of how the cleaning tool is working. Because the operator must have one hand on the control lever of the pipe cleaning machine, the manipulation of the arc of the spiral wire rod described above must be done directly in front of the front end of the machine. Additional sections of spiral wire rod are connected at the rear of the machine.
In the case of the pipe cleaning machine according to DE-PS 27 14 124, the jaw holder is rigidly connected to the hollow shaft and is supported by it in a floating manner outside the machine housing. To hold the coupling jaws, the jaw holder has two recesses, roughly rectangular in cross section, in which two coupling jaws are provided, diametrically opposite each other with respect to the axis of rotation. Via two parallel inclined surfaces, these jaws cooperate with transverse ridges on one side and axially movable pins on the other in such a way that an axial motion is converted to a radial one, as a result of which the coupling jaws are brought into frictional contact with the spiral wire rod. This floating support has the purpose of making it possible to remove the coupling jaws individually for cleaning or replacement without any additional disassembly work.
The removal and insertion of the coupling jaws, however, requires some skill. A great deal of care is also required when the pipe cleaning machine comes with different sets of coupling jaws to accommodate different diameters of spiral wire rods. Although all the jaws have the same outside contour, a jaw of one inside contour may not be matched up with a jaw of a different inside contour. The removal and reinstallation of the coupling jaws is possible only with the help of a pivoting motion, and the coupling jaws must also be secured against flying away under the action of centrifugal force. It is difficult to design the components in such a way that the jaws are easy to remove but cannot at the same time fly outward under centrifugal force. To accomplish this, the known coupling jaws have bumps or projections which engage behind the pins of the actuating device. Whereas slanted planes are provided for the first inclined surfaces, the second inclined surfaces are formed by inclined, longitudinal grooves in only one of the side walls of each of the coupling jaws. This one-sided guidance generates forces which at least encourage the tilting of the coupling jaws. One of the most serious problems of the known solution, however, is that the floating jaw holder, because of its sharp corners and edges, which project a considerable distance from the machine housing, represents a certain danger to the operator. That is, objects can become caught in the relatively irregular surface of the jaw holder as it rotates. It is standard practice to provide a protective housing for the jaw holder, but this makes it even more difficult to replace the individual coupling jaws. In addition, there is nothing to prevent the operator from neglecting to screw on the protective housing.
U.S. Pat. No. 2,940,099 describes a different type of pipe cleaning machine, in which the hollow shaft is divided into two parts inside the machine housing. The ends of the shaft parts facing each other inside the housing are provided with hollow, conical surfaces. These conical surfaces enclose a set of three coupling jaws between them. These jaws are provided at both ends with complementary sector surfaces of a solid cone and are held together only by the hollow conical surfaces and a set of tangential compression springs. The rotary coupling is actuated by pushing the two parts of the shaft together. No separate jaw holder is present. The hollow shaft is not sealed off against the machine housing, and to replace and clean the coupling jaws, the machine housing must be opened or disassembled and possibly cleaned.